The present invention relates to an apparatus and method for mechanically and electrically assembling connector components, such as headers, connectors, and terminal pins, to circuit bearing substrates and, more particularly, to apparatus and method for ensuring the mechanical alignment of terminal pins preparatory to electrical connection of the pins to circuit board traces.
Electrical connectors and headers typically include a housing that supports an array of pins or receptacles with each pin or receptacle having a solder tail that extends rearwardly of the housing to define a corresponding array or field of terminal pins. The printed circuit board to which the connector or header is to be mounted is provided with a corresponding field of holes that corresponds in number and organization with the terminal pin field so that each hole in the printed circuit board accepts a corresponding terminal pin with the distal end of the terminal pins extending a selected distance from the printed circuit board on the side opposite the housing. In general, the distance that the remote end of the terminal pin extends from the surface of the printed circuit board is sufficient to accommodate a solder joint. Usually, soldering is accomplished by wave soldering all the exposed terminal pins to their respective conductive traces on the printed circuit board.
In some applications, it is desirable to mount a header on both sides of the printed circuit board so that the printed circuit board can be engaged from one or both sides. In this type of double-sided application, a header is fabricated with pins having relatively long solder tails. The terminal pin tails are passed through the array of corresponding holes in the printed circuit board with their remote ends extending a selected distance from the opposite side of the printed circuit board. A second housing, termed a shroud, includes an array of holes that correspond in number and organization with the terminal pins extending from the printed circuit board. The shroud is mounted over the terminal pins to effectively define another header on the side of the printed circuit board opposite the first header. In this latter double-sided application, wave soldering cannot be used to effect the soldering of the terminal pins to their respective conductive traces on the printed circuit board since wave soldering would "tin" the entire, exposed portions of each terminal pin. Any solder deposit or residue on the surface of the terminal pin, particularly in the contact zone at the opposite ends of the pin, represents an unacceptable contamination of the typically gold-plated terminal pin surface. In dual-header type applications, soldering of the exposed terminal pins to their conductive traces can be accomplished by hand soldering or, in more sophisticated systems, by placing an annular solder preform over each terminal pin and positioning the solder preform at the base of each terminal pin where it emerges from its bore in the printed circuit board. Once all the solder preforms are positioned, electrical connection is effected by heating the solder preforms to effect the conductive connection of the parts. In general, heating is accomplished with vapor phase reflow devices, ovens, and radiate heat sources.
Various systems have been developed to place the annular solder preform on each terminal pin in the terminal pin field. For example, a horizontally aligned loading tray is provided with a plurality of clearance bores that correspond in number and position with the terminal pins. The annular solder preforms are arranged in rows and columns on the tray in such a way that a solder preform is positioned concentrically over each of the holes. The header is placed on the tray so that each terminal pin passes through a respective solder preform. The loading tray and header are then inverted so that solder preforms slide along their respective terminal pin to provide with a solder preform positioned at the base of each terminal pin.
When each of the terminal pins is straight and properly aligned relative to the other terminal pins, the tip of the terminal pin passes through the annular solder preform without undue surface-to-surface contact that could lead to solder transfer between the preform and the terminal pin. One problem associated with this type of solder preform installation technique is that a bent or skewed terminal pin can impale a solder preform or contact and slide against the preform in such a way that solder is wiped or transferred from the preform onto the typically gold-plated surfaces of the terminal pin. In a worse case situation, the tip of the terminal pin can sever the solder preform as well as subject the terminal pin to compressive forces that can deform the terminal pin or adversely affect its mechanical mounting.